XML — XQuery

What is XQuery?

XQuery is a query language designed for XML data, similar to SQL for databases.

FLWOR Expression

for $book in doc("books.xml")//book
where $book/price > 30
order by $book/title
return $book/title

FLWOR Components

Keyword	Description
for	Iterate over nodes
where	Filter conditions
let	Assign variables
order by	Sort results
return	Output expression

Basic Queries

// Return all book titles
doc("books.xml")//book/title

// Return books with price > 30
doc("books.xml")//book[price > 30]

// Count books
count(doc("books.xml")//book)

String Functions

contains(//title, "XML")
starts-with(//title, "Learning")
substring(//title, 1, 5)

Constructing XML

<results>
{
    for $book in doc("books.xml")//book
    return <book>
        <title>{$book/title/text()}</title>
    </book>
}
</results>

XQuery vs XPath

Feature	XQuery	XPath
Complexity	Full language	Expression only
Logic	Conditional, loops	Limited
Construction	Can build XML	Can't build XML

Mini Practice

1. Write a FLWOR expression
2. Filter and sort results
3. Use string functions
4. Construct XML output

Up Next

Continue with XSLT — transforming XML documents.